Advanced solutions in combustion-based WtE technologies

摘要

Thermal treatment of waste by means of combustion in grate-based systems has gained world-wide acceptance as the preferred method for sustainable management and safe disposal of residual waste. In order to maintain this position and to address new challenges and/or priorities, these systems need to be further developed with a view to energy conservation, resource and climate protection and a reduction in the environmental impact in general. MARTIN GmbH has investigated continuously how the implementation of innovative concepts in essential parts of its grate-based Waste-to-Energy (WtE) combustion technology can be used to meet the above-mentioned requirements. As a result of these efforts, new "advanced solutions" were developed, four examples of which are shown in this article. 1. Radiant superheaters in the first boiler pass. In this process, radiant superheaters are arranged in sections of the boiler where the flue gas temperatures are very high, so as to achieve higher steam temperatures and thus improve the efficiency of the thermal cycle, which in turn increases the production of electric power. 2. Syncom Plus. In the SYNCOM process, combustion air is enriched with oxygen to reduce the flue gas flow and increase the temperatures on the fuel bed, thereby intensifying sintering of the bottom ash. In order to further improve bottom ash quality, a downstream wet mechanical treatment unit (SYNCOM-Plus) is installed to produce granulate. The process achieves higher boiler efficiencies due to a reduced flue gas loss and a high bottom ash quality. 3. Low NO_x processes. The Low NO_x processes help to significantly reduce the content of nitrogen oxides in the flue gas by supplying combustion air/gas in stages and reducing excess air levels. This is achieved by means of primary measures, i.e. the generation of NO_x is prevented to a large extent. If required, NO_x values can be easily reduced even further, down to very low levels, by combining the VLN (Very Low NO_x) and SNCR (Selective Non Catalytic Reduction) processes. 4. Dry discharge of bottom ash. With the dry discharge process, it became considerably easier to recover raw materials (ferrous and non-ferrous metals) from solid combustion residues (bottom ash) and to improve the quality of the latter. In addition, savings can be made in terms of operation and residue disposal as no water is used and the residues to be disposed of contain no water.